1. Field of the Invention
This invention relates to an apparatus for uniformly sprinkling a liquid resin composition, which is useful, for example, in the process of preparing a resinous molding material like a sheet molding compound, a bulk molding compound or the like by mixing a liquid resin composition uniformly with reinforcing fiber.
2. Description of the Prior Art
In copending patent applications, Laid-Open Patent Application Nos. 60-97808 and 61-89810, the present inventors proposed methods for producing resinous molding materials by mixing a liquid resin composition uniformly with reinforcing fiber (e.g., chopped glass fiber).
The methods of the copending applications employs an apparatus which is equipped with a mechanism for sprinkling a liquid resin composition in combination with a feeder for reinforcing chopped fiber, dividing the resin composition into fine droplets and mixing same uniformly with the reinforcing chopped fiber to produce sheets or blocks of molding material continuously.
The sprinkling mechanism is composed of a transfer roller and a sprinkling roller which are disposed in parallel relation with each other and rotated in the same direction, leaving a clearance of 1-3 mm therebetween. The sprinkling roller is formed in a smaller diameter than the transfer roller, and rotated at a high speed of 3,000-10,000 r.p.m. while the transfer roller is put in low speed rotation of 100-1,000 r.p.m.
On the other hand, an outlet of a liquid resin composition feeder is opened over the transfer roller, and a thermosetting or thermoplastic resin composition fed onto the transfer roller from the feeder is moved downward as the transfer roller rotates and handed over onto the sprinkling roller which is located underneath. The resin composition on the surface of the transfer roller is scraped off by air streams which are formed by the high speed rotation of the sprinkling roller, and blown off in the form of globules or short fiber-like fine droplets. As a result, the resin composition which has been carried by the transfer roller is sprinkled from its surface. The sprinkled resin composition is mixed with the reinforcing fiber and, for example simply deposited to form blocks to be sent to a next stage as a resinous molding material. Alternatively it is deposited and shaped into a sheet-like or plate-like form between synthetic resin films which run in parallel relation with each other, while undergoing impregnation, defoaming and so forth before sent to a next stage as a resinous molding material such as SMC, BMC or the like.
In the above-described process, it is the usual practice to employ a resin composition with a viscosity of 200-2,000 poise. However, with a liquid resin composition in such a high viscosity range, it is difficult for the sprinkling roller to loosen and sprinkle the entire amount of the delivered resin composition, and it is often the case that part of the resin composition remains on the surface of the transfer roller as resin composition residues which might impair the uniformity of the resinous molding material to be produced, as will be explained hereinbelow. Namely, if the operation proceeds without completely replacing the deposited resin composition residues by fresh resin composition, the composition will get viscous more and more and finally solidify and block the roller clearance. Upon receiving a certain kind of impact or shock, for example, by the impact of contacting the sprinkling roller, fragments of the solidified resin composition come off the transfer roller surface and mingle into the mixture of the resin composition and reinforcing fiber, lowering the uniformity of the resinous molding material and increasing the defective rate of the molded products to be obtained from the resinous molding material.